Synthesis of epitaxial GaN single-crystalline film by ultra high vacuum r.f. magnetron sputtering method

GaN films were prepared by an ultra high vacuum r.f. magnetron sputtering method, and their crystalline structures depending on total gas pressure, growth temperature, substrate material and film thickness were examined. In X-ray diffraction measurements, GaN film grown at room temperature and gas pressures less than 0.53 Pa, indicated a higher c-axis preferred orientation. When the growth temperature was increased up to 800 °C, crystalline quality of the GaN film was dramatically improved as compared with those prepared at temperatures less than 800 °C. For GaN films on α-Al2O3 (0001) substrates, full width at half maximum values of both X-ray rocking curve for α-GaN (0002) plane and E2 (high) phonon peak at Raman spectra, became narrower than those for GaN films on Si (100) substrates. Moreover, the crystalline quality of GaN film was improved with an increasing film thickness, in the case of α-Al2O3 substrate. A scanning electron microscope image of 1.5 μm thick GaN film surface on α-Al2O3 substrate indicated a number of hexagonal pyramids with six {10-11} facets. The X-ray pole-figure indicated that the GaN film on α-Al2O3 substrate was epitaxially grown single crystal.